Of course the CA has to gain the trust of the users... There are many uses for client-based certificates: code signing, user verification, email encryption, automatic mapping of user account to personal certificates, blah blah blah. The business model of commercial CA's is most certainly not limited to server operators only. While personal certificate stores come with pre-trusted root certificates from many CA's to automatically trust many server-based functions, there is a vast market for client certs.Yes, and how many average users do you know of who know this? I know quite a number of average users and know of absolutely 0 who would be aware of this.
The number of people that you know (or who I know) that are aware of the uses for client
certificates is not what drives commercial certificate authority businessmodels. The simple fact of the matter is that user-level certificates are an important part of the commercial certificate authority plan, and becoming more and more so as your "average" users become aware of certificate applications.
When I got my NIC handle untold years ago, only 561 other humans had one. Your logic would preclude getting one in the first place, since no one knew they existed at the time. When SSL certs were first being created commercially, how many server operators did you know that had one? How many do you know now? It's the same thing with client certs, and the logic stands that certificate applications apply to them as well; particularly in regard to the business and marketing models various certificate authorities are running their business by. That was the point.
t